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You could, but……. A few things to consider first, so that you go into it with your eyes open:

This pump is made for the refrigeration trade. A pump-rate at (atmospheric pressure at sea-level) of 3 CFM is considered modest in the trade, and it will reduce drastically as the pressure goes down. But it depends on how much volume of air you have to pump out of your press. It helps to have a rapid initial removal to fix the work in place so that it doesn’t move as the air pressure takes effect. The pump rate is not constant and reduces as the primary pressure drops.

You will need to find a compatible way of connecting ¼” flare (a specialised refrigeration pipe size and thread) to whatever connection arrangement you have on your press set up. It needs to be absolutely airtight; otherwise you’ll lose your vacuum, so a set of valves in the line is essential to isolate the press when the pump has cone its work. A good vacuum gauge is handy so that you’ll know what is going on in the press.

It’s capable of delivering (they claim) an ultimate vacuum of 5Pa. Essential for evacuating and drying refrigeration systems but a deeper vacuum than you need for basic veneering. A prolonged deep vacuum (overnight or 24 hours, say) may result in premature rapid moisture removal from your stock or the glue if it’s water-based.
To illustrate the point, look at moisture tables for a vacuum. Even at 1 mb, vapour pressure corresponds to a temperature of minus 21 C. To keep the vapour pressure/ temperature above an ambient room temperature (say 20C or 68F) you don’t need a vacuum deeper than 30 mb. That’s less than 1” Hg, (or about 29 “ of vacuum, if you prefer) at sea-level, enough power to press veneer.

Finally It’s oiled. Vac pump oil can be expensive. Additionally, it’s not unknown for the oil to flood out of the pump if the power is interrupted – not always, but it can happen. The discharge can also emit oil mist at high pump-rates.
Oil-less pumps are preferred for this reason.

But, even a single-stage pump at less than $60, it’s very cheap!



Hope this helps...............
 

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A few questions for HandNadeInWood:

Is it normal to run the vac press for 24 hrs? I only did a test with mine and ran it for 1 hr, and it worked fine.

Being as a vac pump removes moisture, could it be used to dry wood, instead of kiln drying? I might take a piece of wood, and bag it, and run the pump for 24 hours, and recheck the moisture.
 

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Consider an alternative: this one at Joe Woodworker is only slightly more expensive, and probably much more suited for your needs. I've had one for 6-7 years now, and so far nary a problem (note: this does not get daily use in my shop). But with this one, you don't have to fiddle around figuring things out, Joe has all the parts and instructions for building a complete press system utilizing this pump. As for your air compressor, I've read those venturi systems pull down a bag much more quickly and that does have some appeal. Since they are less expensive to build, they deserve some consideration. I don't think I'd build one with an oiless compressor...seems like an oil sump model would hold up a little better. I'll chime in on Pirate's question: I typically leave my press run overnight, but that's a function of the glue I use...the plastic resin takes a long clamp time. If you used PVA, you could get by with a lot less press time. I should add: the pump isn't actually running all that time, just cycling to maintain the vacuum.
 

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Hi,

Speaking as a (ex – I’m retired, now) refrigeration engineer, yes it is normal to run it on a refrigeration system for as long as it takes, depending on the internal volume of the unit, and many other factors. We may be talking days or weeks to dry a large fully wet system. There are usually protocols written into agreed work practices for this.

In refrigeration, you run it all the time, for as long as required, but you are using it to remove a heel of old refrigerant gas below atmospheric pressure and ‘non-condensables’ air, nitrogen etc. to obtain an empty system prior to re-charging.
You must presume an absolutely air tight system at this stage of the repair.

Moisture in a cooling system is critical – measured in ppm. If, on the other hand, you are using a vacuum to ‘dry’ (remove moisture at low vapour pressure) a system then you need to control the degree and duration of the vacuum… that can be tricky.

That's using a vac pump in refrigeration.

Pulling a vacuum on a veneer press simply means keeping the air out of a flexible enclosure. If the bag is tight enough to maintain a vacuum (many aren’t, for a variety of reasons) then you can turn the pump off. But the last thing you want is for the thing to loose its vacuum through a tiny leak before the glue is set!

It needs a valve between the pump and the bag to do so. I wouldn't trust a stationary pump to hold pressure from equalising.

Again, the degree of vacuum for the two unrelated purposes is different.

Personally as a wood worker, I experimented with vacuum bags some years ago but I went back to old-fashioned hide glue, cauls and clamps.

I don’t think that you don’t need as high a vacuum for veneer pressing as you do in the refrigeration trade.

As for drying timber, that’s not an area that I’m expert in.
I think it can be done and that the technology already exists, but it is not just the action of removing the moisture… it’s how you can control the rate of removal. Add to that the economics – is it cost effective?
 

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I want to build a vacum press. Can i use a Vacume pump for HVAC.

Like this one? I could use my air compressor. What do you guys think?
I have an old Gast 522 oiled vane style vacuum pump. Small oil container with a wick to lubricate the vanes. My pump is used for a vacuum chuck on my lathe. For my purpose I am looking for decent vacuum rather than flowrate. I am able to pull 28 in vacuum if the wood is not porous.

The refrigeration style you link is likely an oil bath style. A friend recently purchased a similar style and found that the pump creates a lot of oil vapour. Not a problem outdoors, but in his shop he was soon getting a cloud of oil vapour throughout the shop, which is in a downstairs basement so not good ventilation. He had to make a vapour absorber system in order to use the pump.

The pump Fred linked at Joe's woodworking is oilless. No issue with oil, but likely needs to be rebuilt sooner than my oiled vane pump.

The venturi style vacuum generators work, but they consume a lot of air. Overall likely more expensive to run. x HP air compressor vs fraction HP for a vacuum pump.

If you go with a veneer bag, I would not skimp on the bag. The seal of the bag is very important. Joe's woodworking sells kits to build yourself, as well as complete bags.

For the other question about using vacuum to dry the moisture from wood, I have not tried. Likely may work but may depend on the species. The moisture has to be pulled out of the pores. Thin diameter pores and possible that the surface tension of the water in the pores is greater than the vacuum pressure. If this happens, the moisture will not flow through the pores, so no drying. If it did work, it would take a long time.

Like the refrigeration use, the veneer bag or lathe vacuum chuck is recommended to have the vacuum pump run all the time. In theory if the bag had no leaks you could pull the vacuum and unplug. I would not want to trust zero leaks.
 

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Discussion Starter · #7 ·
Thank you for the great info. I wont go with a conpressor type. I will buy a pump and build the rest. Unless you think its a better deal to buy a ready to use setup?
 

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I have no idea whether it's a better deal, but it's certainly enjoyable to build your own, and leaves you in a better position to repair it if something does go wrong down the road. The Joe Woodworker stuff is all first rate stuff, and he offers a very detailed set of instructions on how to do it. If you get lost in the details he also responds to emails personally. One other thing, since Dave mentioned bags. I'd start off with a polyurethane bag. Yep, it may cost twice as much as vinyl, but in the long run is really worth it. The poly bags are more supple and easier to deal with...and Joe has sales on them from time to time that make them a lot less expensive.
 

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When I did a test run, with my a/c vac. pump, I laid out the wood on my assembly table (7' pool table slate) and duct taped a piece of clear vinyl (type used for boat inclosure windows) over it. I installed a screw on, valve stem, in the vinyl, to clamp the vac.hose to. It worked fine.
 
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